In a known manner, an excitation rotary electrical machine, unlike an electrical machine with permanent magnets, can produce engine torque, or supply electrical energy, only when an excitation current is passing through its inductor.
A common type of excitation rotary electrical machine, which is very commonly used in the motor vehicle industry for alternator and starter functions, comprises a rotary inductor and a stator with a plurality of windings.
When the machine is functioning as an alternator, the current which is generated in the windings of the stator by the rotating inductor is rectified such as to supply direct current to the battery of the vehicle.
This voltage depends on the speed of rotation of the inductor, the load connected, and the excitation current.
For motor vehicle applications, the output voltage must be regulated such as to remain constant irrespective of the speed of rotation of the alternator and the charge of the battery.
For this purpose, the output voltage is measured and compared with a set point value by a regulator device which controls the excitation current, such as to minimise any difference.
The company VALEO EQUIPEMENTS ELECTRIQUES MOTEUR has already proposed to carry out this regulation on the basis of sampling measurements by means of digital techniques, which provide substantial advantages in comparison with the conventional analogue methods, in particular in its European patents EP 0 481 862 and EP 0 802 606.
In the design of a modern regulator device, the subjection of the output voltage to a set value is based on the theorisation of a proportional (P) or proportional integral (PI) regulating loop.
The corresponding algorithms adapted to the specifications of the motor vehicle manufacturers can be implemented for example in an FPGA (acronym for Field Programmable Gate Array) associated with an ASIC (acronym for Application Specific Integrated Circuit) which controls the analogue interface with the alternator which has characteristics specific to the component manufacturer, as shown in the article “An High-Voltage CMOS Voltage Regulator for Automotive Alternators with Programmable Functionalities and Full Reverse Polarity Capacity”, P. Chassard, L. Labiste, P. Tisserand et al, Design, Automation & Test in Europe Conference & Exhibition (DATE), 2010, EDDA.
The use of a FPGA makes it possible to implement in particular improvements to the conventional PI regulating loops, such as anti-saturation systems, an example of which is given in the article “Presentation of an Efficient Design Methodology for FPGA, Implementation of Control Systems. Application to the Design of Antiwindup PI Controller”, L. Chaarabi, E. Monmasson, I. Slama-Belkhodja, 28th annual conference of the IECON, 2002, IEEE.
The authors of this last article show that they obtain a response to a scale without overshoot, but do not give any indication as to the return delay in comparison with an open loop.
However, in the field of application to regulator devices for motor vehicle alternators, the inventive body has identified a need for a regulating loop which makes it possible to obtain a return time during a transition from an open loop mode to a linear regulation mode which is short as possible, i.e. to obtain an expected regulated voltage level as quickly as possible.